This invention relates to detecting and classifying faults in an operating machine, and more particularly to detecting and classifying faults in an operating aircraft engine using an Extended Kalman Filter architecture.
Aircraft engines must maintain the highest achievable levels of reliability, because of their extreme safety-critical nature and because the vehicles powered by these engines represent enormous investments in resources. However, as with all machinery, small component failures and other operating faults may occur, owing to material failures, environmental disturbances, and normal deterioration during the operating life of an aircraft engine.
Having faults go undetected and without compensating control actions can risk further damage and may accelerate deterioration, leading to higher safety risks. Similarly, when engine faults are detected by imprecise means and with high levels of uncertainty, operators are often obliged to take the most conservative measures, which typically involve aborting a takeoff or shutting down an engine during flight. Since these measures in themselves pose some risk to the aircraft and its occupants, it is important to be able to distinguish small faults for which more timely and less extreme measures can safely be taken.
Current engine health monitoring schemes detect only large faults and failures of the sensors, actuators, and control hardware. The architecture of the engine controls is based either in dual-redundant or tri-redundant hardware. Much of the diagnostic logic depends on comparing the redundant sensors to each other or to simple static models of the sensor. There is no systematic procedure for taking into account the behavior of the overall system by using a system model in concert with all of the available sensors. This causes current methods to be unable to detect faults until they reach a relatively large magnitude. Current monitoring also detects undesired and potentially damaging engine events like stalls and surges, but does not try to isolate the cause of the event.